Production of nickel pellets



United States Patent Office 3,536,477 Patented Oct. 27, 1970 3,536,477PRODUCTION OF NICKEL PELLETS George Norman Flint, South Ascot, England,and Stanley Charles Townshend, Swansea, Wales, assignors to TheInternational Nickel Company, Inc., New York, N.Y., a company ofDelaware No Drawing. Filed Nov. 16, 1967, Ser. No. 683,466 Int. Cl. B22f9/00 U.S. Cl. 75-5 7 Claims ABSTRACT OF THE DISCLOSURE Carbonyl nickelpellets containing sulfur in controlled amounts and uniformlydistributed throughout, which are particularly suitable for anodes inelectrodeposition of nickel, are produced by decomposing nickel carbonylin the presence of a sulfur-containing gas.

The present invention is directed to the production of nickel pelletsand in particular to the production of nickel pellets by decompositionof nickel carbonyl.

Carbonyl nickel pellets are produced by the well known Mond process inwhich nickel carbonyl is thermally decomposed. The term pellets as usedherein refers to substantially spherical particles which have averagediameters ranging from about 4 millimeters to about 12 millimeters. Thepellets derived from the Mond process are normally nickel of remarkablepurity, every effort being made to prevent contamination by sulfur,since ths reduces the the ductility of nickel. The sulfur content of theMond carbonyl pellets is less than 0.001%

It has now been discovered that the usefulness of carbonyl nickelpellets in electroplating processes can be increased by uniformlyintroducing controlled amounts of sulfur in the pellets.

It is an object of the present invention to introduce controlled amountsof sulfur uniformly throughout carbonyl nickel pellets.

It is a further object of the present invention to provide carbonylnickel pellets which contain controlled amounts of sulfur uniformlydistributed therethroughout.

Generally speaking, the present invention comprises simultaneouslyintroducing nickel carbonyl and a sulfurbearing gas selected from thegroup consisting of carbonyl sulfide and hydrogen sulfide into a movingbed of nickel pellets preheated to at least the decompositiontemperature of nickel carbonyl to produce nickel pellets with sulfuruniformly distributed therethroughout.

The moving bed of preheated nickel pellets can be established inapparatus and in a manner disclosed in UK. Pat. No. 620,287 or asdisclosed in U.S. Pat. No. 3,220,875. It is to be understood that theterm moving bed of preheated nickel pellets includes nickel powder whichis periodically added to nucleate new pellets.

Although other sulfur-bearing gases can be employed, it has been foundadvantageous to employ carbonyl sulfide since the rate of decompositionof carbonyl sulfide and nickel carbonyl are such that the nickel andsulfur are deposited on the pellets in proportion to the amounts of eachgas present. Thus, it is only necessary to introduce a volume ofcarbonyl sulfide calculated to give the desired sulfur concentration inthe pellets. Surprisingly, sulfur dioxide and carbon disulfide arerelatively ineffective.

The effectiveness of pellets as anodes is improved by very small amountsof sulfur introduced in this way, and advantageously the sulfur contentis at least 0.005%. It is to be noted that all sulfur contents givenherein are taken on a weight basis. Higher contents give smootherdissolution but lead to increased non-metallic sludge. Having regard tothis, the sulfur content may be as high as 0.07% or even 0.1% but weprefer it not to exceed 0.03%. The optimum sulfur content of the nickelfor use as anodes is from 0.012% to 0.014%, and to produce this thevolumetric ratio of the nickel carbonyl and the carbonyl sulfideintroduced into the decomposer should be from 4540:l to 3780: 1.

In the Mond process the nickel carbonyl is itself formed by the actionof carbon monoxide on a roasted and reduced nickel matte or othernickel-bearing material, and the carbon monoxide usually circulatesbetween a volatilizer and a decomposer. The use of carbonyl sulfide thuspresents the further advantage that the carbon monoxide produced ondecomposition mixes with that produced by the decomposition of thenickel carbonyl and is returned to the volatilizer without diluting thecarbon monoxide in the circulating gas.

In an advantageous way of carrying out the Mond process the pellets passthrough the decomposer in co-untercurrent to a mixture of nickelcarbonyl and carbon monoxide. In one example gas containing nickelcarbonyl at 70 C. enters a ceramic-lined decomposing chamber containinga mass of nickel pellets which have been preheated in a top compartmentto from about 200 C. to about 240 C. Gas rises from a lower manifold andpermeates the mass of pellets. In the process carbonyl is decomposed andthe pellets are increased in size and are cooled, until they arrive atthe bottom of the decomposing chamber where the temperature is fromabout C. to C. The gas on reaching the top of the decomposing chamber iswithdrawn through an annular manifold. This gas is essentiallynickel-free carbon monoxide and it is returned to volatilizing apparatusin which fresh nickel carbonyl is generated. At the bottom of thedecomposing chamber there is a central opening which is controlled by asliding gate. The nickel pellets pass through this opening into acompartment which has a conical bottom with a central opening from whicha pipe runs. The pellets move down this pipe and drop onto the inclinedbottom of a compartment from which they slide into a collecting chamberat the bottom of a bucket elevator. This takes the pellets up to ahopper from which they enter an inlet pipe and so are returned forfurther treatment to the decomposing chamber via the top pelletheatingcompartment when once again they fall in countercurrent to the risingnickel carbonyl gas. Pellets were produced in this way in an examplewhich will now be given.

The gas mixture contained 8.4% Ni(CO) by volume, equivalent to 210 gramsof nickel per cubic meter, and was fed at the rate of 90 cubic metersper hour. Carbonyl sulfide was introduced into the inlet gas stream atthe rate of 2 liters per hour. Inside the decomposer the temperature ofthe nickel pellets was 200 C. In 24 hours 1000 pounds of nickel pelletsof 0.014% sulfur content were produced.

One advantage of the use of carbonyl sulfide as distinguished from anyother sulfur-containing gas such as hydrogen sulfide is that purging ofthe main carbon monoxide gas circuit between the volatilizer anddecomposer to maintain a high carbon monoxide concentration is kept to aminimum, whereas hydrogen sulfide or other gas gives reaction productswhich have to be purged off together, of course, with some carbonmonoxide.

The main advantage of the introduction of the sulfur into the nickel bymeans of the invention is the uniformity of the distribution of thesulfur with consequent reduction in the amount of sludge when thepellets are used as anodes in the electrodeposition of nickel. Thisadvantage is clearly shown by comparison of the amount of the sludge(both total and metallic) from the dissolution of differentsulfur-containing anode materials in electrolytic processes carried onunder otherwise identical conditions.

Although the present invention has been described in conjunction withpreferred embodiments, it is to be understood that modifications andvariations may be resorted to without departing from the spirit andscope of the invention as those skilled in the art will readilyunderstand. Such modifications and variations are considered to bewithin the purview and scope of the invention and appended claims.

We claim:

1. A process for the production of sulfur-containing carbonyl nickelpellets suitable for use as anodes in the electrolytic deposition ofnickel which comprises simultaneouly introducing nickel carbonyl vaporand carbonyl sulfide gas into a moving bed of nickel pellets preheatedto at least the decomposition temperature of nickel carbonyl to producenickel pellets with sulfur uniformly distributed therethroughout.

2. A process as described in claim 1 wherein the nickel pelletspreheated to a temperature between about 200 C.

and 240 C. are passed downwardly as a moving bed through a decomposingchamber until the pellets are cooled to about C. to C. and the nickelcarbonyl and carbonyl sulfide are passed counter-currently to thedownwardly moving bed of nickel pellets.

3. A process as described in claim 1 wherein the volumetric ration ofnickel carbonyl to carbonyl sulfide is from about 454011 to 3780: 1.

4. Carbonyl nickel pellets which contain at least about 0.005% and lessthan about 0.1% sulfur uniformly distributed therethroughout and whichare characterized by'smooth dissolution and minimal sludge productionwhen employed as anodes in electroplating processes.

5. Carbonyl nickel pellets as described in claim 4 wherein the sulfurcontent is less than about 0.07%.

6. Carbonyl nickel pellets as described in claim 4 wherein the sulfurcontent is less than about 0.03%.

.7. Carbonyl nickel pellets as described in claim 4 wherein the sulfurcontent is between about 0.012% and 0.014%.

References Cited UNITED STATES PATENTS 3,220,875 11/ 1965 Queneau 1171002,881,094 4/1959 Hoover 750.5

L. DEWAYNE RUTLEDGE, Primary Examiner W. W. STALLARD, Assistant ExaminerUS. Cl. X.R. 117-l00

